Oven circulator



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OVEN CIRCULATOR 7 Filed March 8, 1955 4 Sheets-Sheet 4 INVEIQTOR. wffizmUnited rates Patent OVEN CIRCULATOR Robert E. Nelson, Willow Springs,Calif. Application March 8, H55, Serial No. 493,021

3 Claims. (Cl. 107-55) This invention relates to the circulation ofatmosphere in ovens and similar equipment. Although my invention will beshown and described as applied to ovens, it may be applied wherever itis desired to create and maintain an orderly and eificient circulationin an open chamber.

It is well known that the efliciency and uniformity of processes such asbaking which involve contact transferbetween an atmosphere and a productmay be improved by causing the atmosphere to move over the product.Various schemes for obtaining a circulatory movement of the ovenatmosphere have been proposed. Unfortunately, most of those so far triedare either expensive in construction and in application to the equipmentor unsatisfactory in function. For this reason there are at present fewcommercial baking ovens which are well circulated.

The general object of this invention is to provide means for thecirculation of atmosphere in baking ,ovens and like equipment which willbe adequate in function and reasonable in cost, as well as adaptable toa wide variety of equipment.

Most of the circulation means so far proposed depend on the withdrawalof atmosphere from one zone of the oven and its reintroduction intoanother zone at some distance from the first, the circuit beingcompleted by return flow within the oven. in my invention 1 bring thepoints of withdrawal and reintroduction close together, obtaining depthin the pattern of flow within the oven by directing the delivered flowaway from the circulator at high velocity. This flow induces anadditional movement of atmosphere within the oven, giving a total rateof movement greatly in excess of that handled by the circulatordirectly.

In order to insure that the pattern of flow is equivalent over thebaking chamber from side to side, I extend both the collector orWithdrawal means and the flow-directing or delivery means substantiallyto the full width of the baking chamber.

As a means of obtaining a balanced flow and of serving as large aportion of the baking chamber as possible, I usually divide the outgoingflow from the circulator into two parts, each controlling the flow atone side of the circulator.

As installed in the ceiling of an oven my circulator directs itsdelivery close to and parallel with the ceiling, sweeping the bakingchamber immediately below the ceiling continuously and avoiding theaccumulation there of atmosphere at excessive temperature, the source insome poorly circulated ovens of so-called hot spots.

The foregoing method of circulation lends itself to a simple, compactconstruction in which all elements of the circulator are broughttogether into a single unit, inexpensive to construct and to install .bycomparison with other systems offering even passably good results.

Further objects and advantages of my invention will become apparent fromthe description to follow, taken in connection with the drawings,;inwhich:

Figure l is a general viewshowing a circulator unit as installed in atray oven of conventional design, chosen for illustration.

Patented Aug. 12, 1958 Figure 2 is a plan view of my circulator, partlycut away.

Figure 3 is a section taken through the circulator on the line 3-3indicated in Figures 1 and 2.

' Figure 4 is an alternative control shutter detail.

Figure 5 shows an alternative way of joining between the side of thecirculator unit and the ceiling sheets of the oven.

Figure 6 is an alternative detail of the circulator side channel anddelivery ports, a rear view of which appears in Figure 7.

Figure 8 is an alternative form of delivery nozzle construction,incorporating relatively long nozzles.

Figure 9 is a variation on the construction shown in Figure 8.

Figure 10 is a general schematic section taken longitudinally through atray oven such as that of Figure 1.. and shows the positioning of thecirculator and the type of pattern of flow which is produced by thecirculator.

Figure 11 is a similar view through a longer oven, showing the manner inwhich a plurality of units may be employed. For illustration only, theoven shown is of the traveling-hearth type.

Referring first to Figure 1, the numeral 1 indicates the main ordistributor box of my circulator unit, made up of the top 52, sides 51,and ends 59, being completed and carried "by the base unit 16 composedof the bottom sheet 19 and side port channels 50, which join with andare supported by the end carrier angles 20, which may, as in the presentcase, be carried directly upon the side wall structure of the oven,designated generally by the numeral 2. Additional oven structure shownin Figure 1 includes the conveyor trays 23, upper radiator 2 lowerradiator 25, and the outside wall 21.

As shown in Fig. 3, the ceiling sheets 9 of the oven baking chamber aresupported where they join the circulator box 1 by the ledges 26 formedby turning out the lower edges of the side sheets 51.

The junction between the deck 28 of the oven and the outside sheets 8 ofthe circulator may be effected at the angles 27, which may be a part ofthe oven outside structure. The circulator outside sheets extend upwardto join with the circulator deck sheets 17. The insulation 18 of thecirculator is carried over and around the main box 1 and down to joinwith the main oven insulation 22.

Within the main box 1 of the circulator unit is con tained at smallercollector box 11, made up of top 13 and sides 12 and sharing with themain box 1 the ends 59 and bottom sheet 19. The collector intake ports10, also shown in Figure 2, extend across the oven in the bottom sheet19 below the collector box 11, and are purposely madesmall enough tooffer a slight res riction to flow into the collector from the ovenbaking chamber, in order to insure a substantially evenly distributedwithdrawal across the baking chamber.

The fan inlet ring 15 is mounted on top of the collector box 11 at itscenter, and draws from the box equally in both directions from thecenter. The fan wheel 39 is conventional in construction, having aplurality of blades indicated also by the numeral 39 and carried by thehub and back-plate 43 on the shaft 4%, supported by the bearings 42.These bearings mount to the fan drive box 41. End location of the shaft40 is provided by the spacer sleeve 44, which carries the driven sheave45, secured tothe shaft 40, at a definite height above the upper bearing42. The motor oil drives the fanshaft through the drive'sheave 46,driven sheave 45, and belts 47, and is carried by the box 41 through theshelf 63 which supports the motor mounting plate 6.1. This plate ispositioned for'belt adjustment by the four screws '62, acting in nuts64on'the'box 41. The

bearings 42 are protected from excessive heat by the cooling wheel 64,mounted on the shaft 40 below the lower bearing 42.

The fan drive box 41 is supported through the mounting frame 55, whichrides 'onthe main box 1 through the insulating spacer blocks 56. Theframe 55 is bolted through the top of the box 1 and through thereinforcing corner angles 53, which extend within the main box 1between'the side angles 58, to which they are likewise bolted. Rigidityin the location of the fan drive mounting frame 55 is also provided bythe box 1, especially the top 52 and ends 59. Concentricity of the fanwheel 39 and the inlet is obtained after mounting of the fan by shiftingthe inlet 15, which is adjustably bolted to the collector box 11.

The delivery of the fan wheel 39 is directly into the main box 1, whichcarries the flow around the collector box 11 into the spaces 11% formedbetween the lower portions of the sides 51 and the sides 12 of thecollector box, terminating at the bottom 19 and to the delivery ports ororifices 16. These ports are formed in the side channels 50 and deliverlaterally into the baking chamber of the oven, immediately below andparallel to the oven ceiling 9.

Although in many instances no means of controlling the delivery of theoutlet ports 16 is needed, such control is sometimes desirable inspecial situations such as the case in which a row of delivery portsface an opening in the oven structure such as a loading door. in orderto avoid unwanted blowing out of the oven in such a case, the deliveryof the ports affected may be curtailed. The shutter serves thisfunction. It can be adjusted to vary the opening leading to the space110 by moving the shutter toward or away from the wall 51. This isaccomplished through the adjusting rods 31, the ends of which are formedas eyes and fit over the pins 32, secured to the shutter 30. These rods31 need not be moved in or out to the same degree; any desireddifference in the control from side to side of the oven may be obtainedby a differential in rod adjustment. The rods 31 pass out through thetubes 33 and seals 34 to the operating handles 35, permitting adjustmentto be made externally and, if desired, even while the circulator andoven are in operation.

An alternative means of adjustment, offering the advantage of varyingthe effective area of the ports 16, is shown in Figure 4. Thisincorporates a shutter 70, control rods 71 secured to the shutter bysleeves 72, shutter guides 77, tube 73, tube mounting angle 76, seal andlock 74, and operating handle 75. Adjustment is made by raising orlowering the rods 71.

Figure 5 shows an alternative way sheets 9 with the side of thecirculator.

of joining the ceiling Here the side sheet 51 and the ceiling sheet 9are both formed into vertical flanges at 95. The advantage of thisconstruction is in installation, when a considerable amount of verticaltolerance is possible in this joint to take up vertical offsets.

An alternative side channel and port construction is shown in Figures 6and 7. Here the channel 50 is reversed from the position of Figure 3,giving an extended approach to the ports 16. Lateral components of flowthrough the ports 16 are reduced by the guide plates 150.

Figures 8 and 9 show the two alternative channel constructions furthermodified by the addition of formed nozzle-pieces 151 and 152respectively, which further improve the direction of the outgoing flow.

Figure 10 shows the manner of application of the circulator to an ovenrequiring but one unit, such as a small tray oven similar to that ofFigure 1 or the present figure. Here the inside of the oven isdesignated generally by the numeral 2, the outside wall generally by 21,the ceiling by 9, the roof deck by 28, trays by 23 and upper and lowerradiators by 24 and 25.

The circulator unit, using the main box designation 1,

is mounted in the ceiling of the oven, extending across the bakingchamber 2. Oven atmosphere is drawn into the unit through collectorports at 10 and is delivered back into the baking chamber through ports16 below the ceiling level on both sides of the circulator 1.

The normal pattern of flow in each direction from the circulator isdetermined by the direction and strength of the outgoing fiow from theports 16 and by the path of flow available. In this connect-ion it isimportant that the ceiling line, especially near the circulator, besubstantially free of obstructions which could break up the outgoingstream. Given an unobstructed ceiling, I usually consider a distance ofabout 20 feet each way from the circulator, or a total circulateddistance of 40 feet, as the practical limit of effective circulation.

As the high-velocity delivery travels out from the circulator, it mixeswith atmosphere of the baking chamber, which is drawn into the streamand correspondingly diminishes its speed. At the same time the effectivedepth of the stream increases, until the stream breaks down into thelower part of the oven and reverses direction.

Return flow along the lower part of the oven carries the pattern backtoward the circulator. Part of the return flow continues to thecollector of the circulator, while another part passes upward throughthe line of product and joins the outgoing stream directly.

It will be seen that the pattern of flow with respect 'to the product ispredominantly upward nearest the circulator unit and downward at itsextremes.

Figure 11 illustrates the application of several circulator units to alonger oven. As illustrated, three circulators are applied to atraveling-hearth oven having three indirect-fired radiator heatingunits.

Although the disposition of circulator units at about mid-run of eachradiator section is not essential, I. consider it preferable in themajority of cases. Where this i done the spacing of heating sections maydictate the length of oven circulated by each circulator unit, ratherthan the total potential of the circulator.

Radiators near the ceiling of the oven do not interfere with theeffective use of my circulator, provided the circulator is so located ineach case as to avoid breaking up of the essential outgoing stream byobstacles such as headers. The location of headers near the collectorintake ports is not a handicap unless the closeness is such as actuallyto throttle the flow. Since, in the general case, the tubes of aradiator are substantially parallel with the initial direction of flow,they offer no real obstruction to an effective pattern of circulation.

Iclaim:

1. A circulator for ovens and like equipment having an open processchamber including a ceiling thereof, comprising a power-driven fan orblower, a collector box in said ceiling extending transversely thereofand communicating with the inlet of said fan or blower, a distributorbox communicating with the outlet of said fan or blower and having a topand sides surrounding said collector box in spaced relationship to thetop and sides thereof, and delivery means into said process chamberconnecting with the lower portions of the spaces formed between thesides of said distributor box and said collector box.

2. Structure according to claim 1, said delivery means being below saidceiling and adapted to deliver laterally into said process chamber.

3. Structure according to claim 1, said delivery means being adapted todeliver laterally into said process chamber close to and parallel withsaid ceiling.

References Cited in the file of this patent UNITED STATES PATENTS2,236,085 Cook Mar. 25, 1941 2,554,239 Cauliield et a1. May 22, 1951FOREIGN PATENTS 500,691 Belgium Feb. 15, 1951

